Apparatus with force isolation for measuring weight of collected fluid and method

ABSTRACT

A urinary output monitor for determining the volume of fluid in a urinary collection bag during the collection process having a weighing apparatus for weighing the contents of a collection bag and means for substantially isolating the end of a drainage tube from applications of significant forces to the collection container. The isolation mechanism is incorporated into the container assembly in the form of a conduit for interconnecting an inlet connector and an outlet connector which has sufficient flexibility to preclude it from conveying any significant force in a direction along its length which would adversely affect the weight measurement. Since varying forces applied to the weighing apparatus by drainage tube connectors of different catheters are eliminated by the isolation mechanism, fluid entered after offset determination for zeroing the weighing apparatus to compensate for bag weight is included in the total measurement.

BACKGROUND OF THE INVENTION

This invention relates to apparatus for weighing collected fluid duringthe collection process and, more particularly, to means for isolatingthe weighing mechanism from coupling forces of the fluid collectionsystem and a method of using same to obtain improved accuracy in weightmeasurements.

Various apparatus are known for determining the urinary output of apatient which is measured in units of volume. In U.S. Pat. No. 4,448,207of Parrish, the height of fluid in a collection container is determinedthrough ultrasonic echo sensing, and then the volume is calculated by acomputer based upon a stored volumetric profile of the collectioncontainer and the determined height. Similarly, in U.S. Pat. No.4,051,431 of Wurster, the level of a fluid in a container is determinedby means of capacitive sensing from which the volume can be determinedin a rigid container. In U.S. Pat. No. 4,314,484 of Bowman, an opticaldrop count apparatus first forms drops from the collected fluid ofapproximately a known uniform volume and then counts the drops todetermine the total volume accumulated. A similar apparatus is alsoshown in U.S. Pat. No. 4,291,692 of Bowman et al., 4,347,316 ofJesperson and 4,286,590 of Murase.

Other techniques of measurement are also known. In U.S. Pat. No.4,417,585 of Franck, moveable measurement containers are alternatelyfilled and dumped in a collection container, and the volume iscalculated by measuring the number of fill and dump cycles. Similarly,in U.S. Pat. No. 4,206,767 of Winegrove, a plurality of measurementtubes are successively filled and sensed to determine volume.

It has also been known to weigh the collected fluid and to determine thevolume from the weight. The weight and thus volume is determined in U.S.Pat. No. 3,583,400 of Menhardt by means for moving the collection fluidand determining the momentum of the fluid from which the mass ofcollected fluid is calculated. In an article by N. J. Randall, entitled"A New URO Flowmeter for Routine Clinical Use" in the January, 1975issue of Biomedical Engineering (London), a simple strain gaugetransducer system associated with a cantilever beam is employed to makedirect weight measurements. A special tube is provided to absorb andredistribute urine flow into the container to prevent momentum duringflow from effecting the weight measurement.

It is also known to use the weight measurements of collected fluid tocontrol the fluid collection process itself. For instance, in U.S. Pat.No. 3,583,400 of Menhardt, a switch controls fluid flow in a collectioncontainer in resonse to measurement of collected fluid. Weight is usedto stop a blood collection process when the amount collected exceeds apreselected weight in an apparatus shown in U.S. Pat. No. 3,977,567 ofRudd. In U.S. Pat. No. 4,390,073 of Rosen, blood in a collection bag isweighed to control collection.

While other approaches for work, the measurement of weight to determinevolume is preferred. However, volumentric measurements based on weighingthe collected fluid chamber can be no more accurate than the accuracy ofthe weight measurement itself. Therefore, it is important to make surethat it is only the weight of the fluid being measured and not theweight of the container or the forces associated with the collectionsystem connected with the container which can affect the weightmeasurement. One of the advantages that weighing has over other methodsof volume measurement is that the measurement does not require a specialrigid container for level sensing and can be used after collection hascommenced or after it is complete. In known systems which measurevolume, however, because of the accuracy problem caused by variableforces applied by the upstream collection systems attached to thecontainer, initial amounts of fluid collected in a bag uponcatherization and before the bag is attached to the weighing apparatusare not measured in order to zero the weighing apparatus. This is doneto partially offset some of the error introduced by the error producingforces applied by the force isolation system against the container.

SUMMARY OF THE INVENTION

It is therefore the primary object of the present invention to provideapparatus with a forced isolation system that overcomes theaforementioned problems with known weighing apparatus and a method ofusing same to measure all collected fluid including the fluid collectedbefore attachment of the collected fluid container to the weighingapparatus.

The objective is partially achieved through provision of an apparatusfor measuring the weight of fluid entering a container of a systemobtained from the downstream end of a fluid drainage tube includingmeans for substantially mechanically isolating the end of the tube fromthe collection container. This apparatus includes a weighing apparatushaving a frame and a weighing mechanism which moves relative to theframe during changes of the weight being weighed thereby and means forconnecting the container to the weighing mechanism to be weighedthereby. The container moves with the weighing mechanism relative to theframe as increasing amounts of fluid are introduced into the container.Means are provided for holding the downstream end of the tube againstmovement relative to the frame and for coupling the drainage tube withthe container for relative fluid communication therewith. This couplingmeans includes means for substantially mechanically isolating the end ofthe tube from application of significant force to the container wherebythe accuracy of the measurement of the weight of the container and itscontents is not significantly affected by the coupling means.

In a preferred embodiment, the isolation means includes a flexiblemember interconnecting the end of the drainage tube to the containerwhich is not capable of transferring any force therebetween of anysignificance. The container can be a flexible bag and includes meansattached to one of the pair of connectors for suspending it from theweighing mechanism to move therewith.

The objective of the invention is also achieved through provision of acontainer assembly for biological fluids, comprising, a hollow containerbody having an inlet opening for receipt of fluids therewithin, an inletconnector for connection with the end of a drainage tube, and means forsubstantially mechanically isolating the container body at the inletopening from relative movement of the inlet connector. The isolatingmeans includes a flexible conduit for interconnecting the inletconnector and inlet opening, and the conduit has a flexibilitysufficient to prevent it from mechanically conveying significant forcein a direction along the conduit.

Because of the improved accuracy obtained through isolation, an improvedmethod of measuring the total volume of all the fluid collected into acollection container, including that fluid collected before attachmentto the weighing mechanism, is provided. This method comprises the stepsof predetermining the weight of a fluid container, offsetting thedetermined weight of the container from a weighing apparatus to zero theweighing apparatus, connecting the downstream end of a drainage tube toan inlet opening of the fluid container by means for substantiallymechanically isolating the container and the weighing apparatus fromforces due to the interconneciton of the container and the end of thetube, attaching the container to the weighing apparatus to be weighedthereby, entering into the container the fluid to be weighed through thedrainage tube and said isolation means and weighing the container andfluid therein. Preferably, the method also includes the steps ofentering some of the fluid into the container after determining theamount of offset to zero the weighing apparatus to compensate for theweight of the container and before the step of attaching the containerto the weighing apparatus to be weighed thereby and then obtaining fromthe weighing apparatus the combined weight of the fluid entered into thecontainer before and after the step of attaching the container to theweighing apparatus prior to further zeroing of the weighing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects, features and advantages of the present inventionwill be described in greater detail and further objects and advantageousfeatures will be made apparent in the following detailed description ofthe preferred embodiment which is given with reference to the severalfigures of the drawing, in which:

FIG. 1A is a perspective view of an automated urine output monitor, orAUOM, for weighing and making other measurements of urine collected in aflexible urinary collection bag releasibly attached thereto and withrespect to which a preferred embodiment of the present invention isemployed;

FIG. 1B is another perspective view of the AUOM of FIG. 1A but with theurinary collection bag and a front panel removed to facilitate a betterview of the inner workings of the AUOM;

FIG. 2 is a plan view of the AUOM of FIGS. 1A and 1B showing the AUOMdisplay and control panel;

FIG. 3 is an enlarged front view of a header assembly and forceisolation and sampling apparatus connected with the urinary collection;

FIG. 4 is a plan view of the header assembly of FIG. 3;

FIG. 5A is a sectional side view taken along section line VA--VA of FIG.3;

FIG. 5B is a sectional side view identical to that of FIG. 5A but withthe header assembly in a relatively lower position due to increasedweight of the collected urine;

FIG. 6 is an enlarged perspective view of the force isolation andsampling chamber assembly of FIGS. 1A, 4, 5A and 5B;

FIG. 7 is a plan view of the header mounting mechanism of FIG. 1B;

FIGS. 8A and 8B are schematic illustrations of an alternate embodimentof the force isolation system of FIGS. 5A and 5B under relativelyunloaded and loaded conditions, respectively;

FIGS. 9A and 9B are schematic illustrations of another alternateembodiment of the force isolation system under relatively unloaded andloaded conditions, respectively;

FIGS. 10A and 10B are schematic illustrations of a further alternateembodiment of the force isolation system under relatively unloaded andloaded conditions, respectively;

FIGS. 11A and 11B are cross sectional and perspective illustrations ofstill another alternate embodiment of the force isolation system; and

FIG. 12 is a sectional side view of an alternate embodiment of the forceisolation system.

DETAILED DESCRIPTION

Referring now to the several figures of the drawing, particularly FIGS.1A, 1B and 2, an automated urine output monitor, or AUOM, 20 is seenwith a flexible, plastic urinary collection bag mounted thereto by meansof a sampling chamber assembly 24 and a force isolation system 26. Aswill be explained in greater detail, the sampling chamber assembly 24and force isolation system 26 interconnect to form a closed fluidcollection system between a patient (not shown) connected to the distalend of a Foley catheter 28 and the interior of the urinary collectionbag 22. The catheter 28 is connectable by means of a catheter connector29 and connector 31 with flexible, plastic drainage tube 30. The otherend of the drainage tube 30 is in fluid communication with the samplingchamber assembly 24 by means of a suitable tube connector located atopsampling chamber assembly 24. Fluid from sampling chamber 24 flowsthrough a flexible conduit of the force isolation system 26 and throughan angular conduit 32 of a front entry connector assembly 34.

Referring to FIG. 1B, the AUOM is seen to have a housing, comprised of ahousing frame 36 with a removable front housing panel 38. This housingprotectively encloses an electronic control and measurement module 40which includes a computer and interface circuitry. The computer receivessignals through the interface circuitry from suitable transducersassociated with sensor probe assemblies 42 and 44 connectible with thesampling chamber assembly 24 for noninvasively determining both specificgravity and temperature of a urine sample contained within the chamberassembly 24. The computer is also responsive to electronic signalsreceived through other interface circuitry from transducers associatedwith a pair of mounting arms 46 and 48 of a bag mounting assembly 50 todetermine the weight of the urine collected within urinary collectionbag 22. The computer also determines core temperature based on signalsfrom a temperature transducer associated with a core temperature probewithin catheter 28 and connected thereto by means of an electrical cord52. The computer also receives signals through suitable transducersindicative of the ambient temperature, the status of its D.C. portablebattery supply (not shown) and signals from a control section 54 of acontrol and display panel 56, FIG. 2. These controls include a manuallyactuatable reset switch 58, a start switch 60, a temperature scaleselection switch 62 and a display light actuation switch 64.

Referring to FIG. 2, the computer automatically, periodically calculatesspecific gravity, temperature, volume and time based upon thesetransducers and control input signals and causes them to be visuallyindicated at various electronic digital display units of a displaysection 66 of control and display panel 56. The volume in milliliters ofthe urine collected in bag 22 for the present hour, the previous hourand for all collection accumulated is indicated at display units 68, 70and 72. Based upon appropriate signals received from either the startswitch 60 or reset switch 58, and an internal clock, the computer alsoindicates the number of minutes elapsed since the present hour commencedand the cumulative time since the collection process started at displayunits 74 and 76, respectively. The specific gravity is shown on displayunit 78, and core temperature, either in Fahrenheit or centigradedegrees depending upon the state of scale selection switch 62, is shownat display unit 80. A low battery condition for the portable AUOM isprovided by an indicator 82, and various conditions sensed by thecomputer are indicated by an alpha numeric message display unit 84 andan alert indicator lamp 86.

Further information concerning the operation of the computer,transducers and other aspects of the AUOM unit 20 may be obtained byreference to the U.S. patent application of Brian H. Silver entitled"Electronic Biological Fluid Output Monitoring With NoninvasiveSensing", U.S. patent application of Frank W. Ingle and Alan R.Selfridge entitled "Biological Fluid Specific Gravity Monitor withUltrasonic Sensor Circuit", and U.S. patent application of FredRasmussen entitled "Ultrasonic Sensor", all filed contemporaneouslyherewith and assigned to the assignee of this application.

In normal operations, the AUOM unit is releasibly attached to an uprightmounting standard 90 by means of a screw clamp 92 attached to the backof housing 22. Although standard 90 may be mounted to its own floorsupported base member 93, as shown, preferably standard 90 is releasiblymounted to the patient's bed in a manner shown in U.S. patentapplication of James R. Gross, entitled "Medical Equipment MountingApparatus" filed contemporaneously herewith and assigned to the assigneeof this application.

The catheter set, consisting of catheter 28, catheter drainage tube 30,sampling chamber assembly 24, force isolation system 26, front entryconnector assembly 34 and collection bag 22 are brought to the patientand the patient is catherized. After the AUOM unit has been mounted in acorrect location for the patient and after the catherization procedure,the urinary collection bag 22 is taken to the AUOM unit 20 which islocated outside of the sterile field of the catherization site and ismounted to the AUOM unit. The force isolation system 26 includes arelatively rigid header assembly 94 having a pair of spaced femaleconnectors 96 and 98 which are adapted for mating receipt of mountingarms 46 and 48, respectively, to suspend the collection bag 22therefrom. As will be explained in greater detail below with referenceto FIG. 7, means are provided for causing arms 46 and 48 to interlockwith female connectors 96 and 98.

After a pair of protective sensor caps 102, only one of which is shownin FIG. 3, are removed from a pair of probe guide connectors 104 and106, the probe quide connectors 104 and 106 are enabled for matingreceipt of sensor probe assemblies 42 and 44, respectively. Once caps102 are removed, the sampling chamber assembly 24 is enabled for receiptwithin a sensing location 108 with sensor probe guide connectors 104 and106 located respectively opposite sensor probes 42 and 44. Thecollection bag 22 is then locked onto arms 46 and 48.

The two sensor probe assemblies 42 and 44 are then caused to movetogether through manual actuation of a probe actuator 110. When theactuator 110 is moved from its position as shown in FIG. 1B to theoperative position shown in FIG. 1A, the two sensor probes move togetherand respectively matingly engage the sensor probe guide connectors 104and 106. Since the drainage tube 30 is mounted to sampling chamberassembly 24, both it and the downstream end of the drainage tube 30 areheld against any movement relative to the housing frame 36. After thisis done, the start switch 60 is actuated and the AUOM unit 20 beginsoperations to provide the monitor information described above.

The details of the force isolation system 26 and the sampling chamberassembly 24 are described with reference to FIGS. 3, 4, 5A, 5B, 6 and 7.

Referring particularly to FIGS. 3 and 4, the header assembly 94 is seento comprise a central body 111 with a central force isolation headerconnector 112 located between the pair of female connectors 96 and 98together with a pair of opposed header mounting arms 114 and 116. Theheader is secured to the flexible bag 22 by means of a pair of headermounting pockets 118 and 120 within which are held mounting arms 114 and116, respectively. These pockets are formed from extensions of the backand front walls 130 and 128 of urinary collection bag 22 which aresecured together along a common seam 122 and a pair of upper seams 124and 126 respectively associated with header mounting pockets 118 and120. During manufacture, the header assembly 94 is placed in positionwith its header mounting arms 114 and 116 between the front and backwalls of collection bag 22 prior to the formation of seams 124 and 126.Alternately, if sufficient clearance is provided or the relatively rigidheader assembly arms 114 and 116 are sufficiently flexible, the arms 114and 116 are inserted into pockets 118 and 120 after all the seams areformed.

Referring also to FIGS. 5A and 5B, a front wall 128, opposite a backwall 130 of urinary collection bag 22, is seen to have an inlet opening132 in fluid communication with a coupler 134. Coupler 134 is sealed tothe front wall 128 of flexible bag 22, by means of a flexible peripheralmounting collar 135 which is sealed to the front wall 128 around theperiphery of inlet 132. A fluid conductive connector assembly, whichforms part of the force isolation system 26, includes a downturned,elongate portion, or angular conduit, 138 for making fluid connectionwith the front 128 of the flexible bag 22 through coupler 134 and inlet132. This angular conduit 138 is in fluid communication with a hopperportion 140 of relatively larger diameter, a shoulder 142, a flexiblediaphragm mounting portion 144 and a movement restraint portion 146.

As seen, the angular conduit 138 extends at an acute angle relative tothe back wall 130 of the collection bag 122. This enables it to makeconnection with the coupler 134 at a location offset from the centralvertical plane of symmetry of the bag. This is the location that theportion adjacent coupler 134 of the wall 128 would move to as the bag 22became full if there were not restraint on its movement. Otherwiseduring filling asymmetrical backward bulging of the collection bag 22would result because of wall 128 being held at the vertical plane by theconduit 138.

This bulging would undesirably require more clearance between the AUOMhousing panel 38 and the collection bag 22. The coupler 134 has acoupler axis 148 which extends in a direction substantially parallel tothe front of the bag at the peripheral collar 135. A first member 150has an axis 152 which extends at a right angle relative to the front ofthe bag at mounting collar 135. The connector portion 154 associatedwith axis 148, on the other hand, extends in a direction substantiallytransverse to that of the first portion 150 to form a right angleconnection. As best seen in FIG. 5B, the axis 148 also forms an obtuseangle with the central axis of hopper portion 140 and connector 112.

During assembly, the angular conduit 138 and hopper portion 140 arereceived through the central force isolation connector 112. The headerconnector 112 is a cylindrical female connector for mating receipt ofthe cylindrical wall of the hopper portion 140. In order to preventrelative rotary movement, however, the cylindrical wall of headerconnector 112 has an interlock notch 156, as best seen in FIG. 4, whichis adapted for mating receipt of a mating interlock member 158 seen inFIGS. 5A and 5B. The mating interlock member 158 is carried on the sidewall of hopper portion 140 and is snugly received therein to preventrelative rotary movement between the hopper portion 140 and the centralforce isolation connector of header assembly 94. In addition, since onlya single asymmetrically located interlock notch 156 and interlock member158 are provided, the hopper portion 140 and the central force isolationheader connector 112 are thereby keyed to require their intercoupling ina preselected orientation relative to the inlet 132.

After full insertion, the coupler 134 is pivoted upwardly for matingreceipt of the open end of the angular conduit 138. After thisconnection is made, the interconnections between the connector 112 andhopper portion 140, connector 112 and shoulder 142 and connector portion154 and the distal end of angular conduit 138, are rendered permanent bythe application of adhesive, by setting of previously applied adhesiveor by heat fusion or solvent bond.

Thus, the fluid conductive connector assembly 32 is permanently andfixedly attached to the urinary collection bag 22. It thereby forms afirst relatively rigid connector for connecting one end of a highlyflexible diaphragm, or conduit, 164 to form part of the force isolationsystem 26. As will be explained, the other part of the force isolationsystem comprises means for holding and interconnecting a downstream openend 166 of drainage tube 30 to the other end of flexible diaphragm 164and for holding the drainage tube end 166 fixed relative to the housingframe 36.

In the instant case of the preferred embodiment, the relatively rigidconnector for connecting the distal end 166 to the end 168 of theflexible diaphragm 164 includes a sampling chamber assembly 24 and meansassociated therewith. However, it should be appreciated that thesampling chamber function is not necessary to achieve force isolationand in the absence of such a chamber, a simpler connector may beemployed for connection of the drainage tube downstream open end 166 tothe upstream end of the flexible diaphragm.

Since the end 166 of drainage tube 30 is held firmly, the collection bagis isolated from force applied thereto. The high degree of flexibilityof the diaphragm 164 prevents the connection thereof with the collectionbag 22 from applying any significant restraint or other force thereto orto the weighing apparatus to which it is attached. Briefly, samplingchamber assembly 24, as seen, has a sampling chamber 170 containedwithin a sampling chamber housing 172 intermediate a housing inlet 174and an outlet 176. The inlet 174 is connected in fluid communicationwith the open end 166 of drainage tube 30 by means of an annular inletconnector 178. After the flexible drainage tube 30 is inserted intomating relationship with connector 178, the connection is renderedpermanent by means of applying adhesive, causing preapplied adhesive toset, by solvent bond or the like. Urine dripping out of the inlet 174falls into a combined inlet and outlet opening 180 of sampling chamber170. After the sampling chamber 180 is filled, additional urine fallinginto the open top 180 will both mix with the previously collected urinein the sampling chamber and will cause other urine to overflow and fallthrough the outlet 176 and into hopper portion 140 of connector 136.

The outlet 176 is connected through an elongate conduit 182interconnected at its distal end with a diaphragm connector 184. Theflexible diaphragm 164 comprises a thin, flexible moisture imperviousmaterial, such as thin rubber, animal membrane, or the like, which formspart of a closed fluid collection system between the end 166 of drainagetube 30 and the collection bag 22. It has a relatively large inletopening at the ends of a mounting collar 186 which is resilientlysecured around the annular diaphragm mounting portion 144 of theconnection assembly 32. At its other end, it has another annular collar188, opening in a direction opposite to that of collar 186 and having arelatively smaller diameter to resiliently fit around the end of adiaphragm connector 184. A concave flexible wall interconnects collars186 and 188.

The force isolation system 26 operates as follows. When the collectionbag 22 is mounted to the header assembly 94, it is fixedly held to arms46 and 48 which, in turn, are connected with a weight transducer whichresponds to the total force imposed upon arms 46 and 48. Ideally, thistotal force corresponds only to the weight of the fluid contained in theurinary collection bag 22 and the weight of the collection bag 22 itselfwhich is known and can be offset to precisely calculate the weight ofthe urine alone. However, the urinary collection bag 22 must beconnected to the end 166 of the drainage tube for receipt of the urine,and in the absence of a force isolation system, forces are imposedthrough the drainage tube 30 which are transmitted to arms 46 and 48 andthereby introduce error into the weight calculation.

The arms 46 and 48 are caused to move downwardly by the weight of theurine being collected, but the end 166 of drainage tube 30 is heldstationary relative to the housing frame 36 of the AUOM unit 20 by meansof the mating insertion of sensor probe guides 42 and 44 within guideconnectors 104 and 106. Thus, forces applied to the end 166 of thedrainage tube 30 are borne by the AUOM unit 20 and they are nottransmitted to the header assembly 94. The flexible diaphragm 164 isthen the only element which can transmit extraneous forces through theweighing mechanism. However, the flexible diaphragm is purposelyselected to be so flexible that it is not capable of sustaining orsupporting any significant forces either in a direction along itsprincipal axis of movement coincident with the elongate axis of conduit182. It can be maintained in a relatively stable state in any of severalrelative positions without transmitting any significant force along itslength. Accordingly, the mounting arms 46 and 48 and collection bag 22are free to move relative to the frame 36 in substantial isolation fromany forces from the urinary delivery system from the patient to thecollection bag 22.

Referring particularly to FIGS. 5A and 5B, when the collection bag 22 isfirst attached, the relative location of the mounting arms 46 and 48relative to the sampling chamber assembly is as shown in FIG. 5A. Asseen, the underside surface 192 of sampling chamber housing 172 restsatop restraint portion 146 of connection assembly 32. However, after thesensor probe assemblies 42 and 44 are engaged with the sampling chamberassembly 24, the underside surface 192 is held thereby slightly aboverestraint portion 146. However, as urine is added to the collection bag22 and its weight increases, the mounting arms 46 and 48 and thusconnector assembly 136 attached thereto, move downwardly away from anunderside surface 192 of sampling chamber housing 172, causing the inletopening at diaphragm collar 186 to move closer to the outlet opening atdiaphragm collar 188. This relative movement is not significantlyresisted by the concave wall 190 which forms a downwardly facing cuffwithin the space 195 between shoulder 142 and restraint portion 146, asshown in FIG. 5B, in response to this relative movement. This cuff movesalong the length of the concave wall 190 of flexible diaphragm 164 asthe connectors 144 and 184 are moved relative to one another.

Referring still to FIGS. 5A and 5B, particularly FIG. 5A, the diaphragmconnector 184 carries a stop member 194 which is engageable in blockingrelationship with the underside 196 of restraint portion 146 to restrainrelative movement between the inlet and outlet connectors of theflexible diaphragm 164 beyond a preselected limit. Movement beyond thislimit would cause the transmission of force to the header assembly 94through means of the connector assembly 136 or which would stretch orotherwise damage the flexible diaphragm 164.

As best seen in FIG. 6, the force isolation system 26 also includesmeans for restraining relative rotary movement between the ends of theflexible diaphragm which would twist it beyond a preselected limit. Therotary restraint is provided by means of a pair of radial blockingmembers 198 and 200 fixedly attached to the elongate conduit 182 ofsampling chamber assembly 24 and received within a pair of slots 202 and204. Slots 202 and 204 are formed by a pair of opposed arcuate sections206 and 208 of restraint portion 146. Each of arcuate sections 206 and208 define a pair of rotary blocking surfaces 210 and 212 at oppositesides of slots 204 and 202 which are spaced from one another by apreselected amount corresponding to the preselected limit. The blockingsurfaces prevent the radial blocking members 198 and 200 associatedtherewith and thus the flexible diaphragm 164 from rotary movementbeyond the preselected limit.

Referring now to FIG. 7, the detailed features of mating relationshipbetween the female connectors 96 and 98 of header assembly 94 with themounting arms 46 and 48 and other features of the bag mounting assembly50 will be described. Each of the arms 46 and 48 are mirror images ofone another and have a manually engageable portion 220 which extendthrough the associated female connector 96 and 98 for access at thefront of the collection bag 22. Both of arms 46 and 48 are made ofrelatively resilient material and the distance d between a pair ofoutwardly facing planar cam surfaces 238 and 240 of arms 46 and 48, whenin a neutral, or unflexed, condition, is greater than the distance Dbetween a pair of inwardly facing interlock surfaces 226 and 228 offemale connectors 96 and 98, respectively. A pair of shoulders 242 and244 are formed at the edge of each of the outwardly facing planar camsurfaces 238 and 240 and a pair of interlock surfaces 222 and 224 ofarms 46 and 48, respectively, which matingly receive the associatedinterlocking surfaces 226 and 228. When female connectors 96 and 98 areslid over the manually accessible portions 220 of arms 46 and 48,arcuate caming surfaces 234 and 236 carried thereby respectively engageinterlock surfaces 222 and 224 and are thereby gradually, resilientlycammed together until the distance between outwardly facing planar camsurfaces 238 and 240 is equal to the distance D. The planar cam surfaces238 and 240 then ride the interlock surfaces 226 and 228, respectively.When the lagging edges of interlock surfaces 226 and 228 pass shoulders242 and 244, the arms 46 and 48 resiliently snap apart with the matinginterlock surfaces joined as shown. The shoulders 242 and 244 then abutagainst the edge of their associated female connector interlock surfacesto prevent removal of the connectors from the arm. Thus, to mount theheader assembly to arms 46 and 48, the female connectors only need to beslid on to their associated arms to automatically move them to aninterlock position from their release position until the armsresiliently snap into the interlock position, as shown in FIG. 7. Oncethis occurs, a pusher member 248 resiliently pushes shoulders 243 and245 of the female connectors against shoulders 242 and 244 of the arms.

The female connectors are automatically disengaged from the arms 46 and48 when the manually engageable portions 220 of arms 46 and 48 aresqueezed together sufficiently to move shoulders 242 and 244 out ofblocking engagement. These shoulders, or blocking edges, 242 and 244resist resilient biasing of the header assembly and female connectorsthereagainst provided by a coil spring 246 associated with a pushermember 248 mounted within a cylindrical housing 250. This pusher membercauses the female connectors 96 and 98 to automatically, slideably moveoff of interlocking engagement with arms 46 and 48 when the distancebetween cam surfaces 238 and 240 is less than the distance D between theinterlock surfaces 226 and 228 of the connectors. Thus, the connectorsare automatically disengaged from arms 46 and 48 simply by manuallysqueezing the manually accessible portions 220 together from theinterlock position to the release position.

Referring to FIGS. 8A through 11B, alternate embodiments of the flexiblediaphragm and associated connectors of the force isolation systems areschematically illustrated. In FIGS. 8A and 8B, a flexible diaphragm 252is shown with an inlet 254 and outlet 256 of approximately the samediameter and which has substantially straight walls rather than concavewalls, as in the preferred embodiment of FIGS. 4, 5A and 5B. An inletconnector 258 is held to the frame and connected to the drainage tube166 and an outlet connector 260 is connected to the collection bag 22(not shown). In addition, as best seen in FIG. 8A, 258 and 260 when thecollection bag is relatively empty, the flexible diaphragm 252 forms acuff 262 which faces upwardly toward the inlet connector 258. As thecollection bag 22 fills, the outlet connector 260 moves downwardlycloser to the inlet connector 258, as shown in FIG. 8B.

Referring to FIG. 9A and 9B, another embodiment of a flexible diaphragm264 is shown under circumstances of a relatively empty and relativelyfull urinary collection bag 22, respectively. In this embodiment, theflexible diaphragm 264 has an upturned mounting cuff 266 which matinglyreceives an annular outlet connector 268 and the inlet end of flexiblediaphragm 264 has a collar 270 connected to an inlet connector 272 oflesser diameter than outlet connector 268. A downwardly turned cuff 274is formed in flexible diaphragm 264 which is gradually removed as theconnectors 272 and 268 separate as shown in FIG. 9B until, at fullextension, the flexible diaphragm 264 has a conical shape, as shown inFIG. 9B. Unlike the embodiments of FIGS. 8A and 8B and FIGS. 5A and 5B,the inlet is located above the outlet in the embodiment of FIGS. 9A and9B.

Referring now to FIGS. 10A and 10B, another embodiment of a flexiblediaphragm 276 is shown in which an inlet end is connected to an inletconnector 278 by means of a collar 280, and the outlet end has a collar282 which is held between a pair of outlet connector members 284. Anupturned cuff 286 faces the inlet connector 278, and when the flexiblediaphragm 276 is extended, as shown in FIG. 10B, the cuff 286 movesupwardly until a conical configuration is obtained, as shown.

Referring now to FIGS. 11A and 11B, yet another embodiment of a flexiblediaphragm 288 is shown similar to that of FIGS. 10A and 10B but in whichthe body of the flexible diaphragm is bell shaped when extended, asshown in FIG. 11B, and which has a laterally extending collar 290attached to a laterally extending outlet connector 292 instead of thevertically extending collar and outlet connector of FIG. 10A. Like FIG.10A, an upturned cuff 294 is formed when the inlet connector 292 and anoutlet connector 296 are spaced from one another as shown in FIG. 11A.

Referring to FIG. 12, a schematic illustration of yet another embodimentof the force isolation system 26 is shown in which the flexiblediaphragm 298 is generally cylindrical and does not form either anupturned or a downturned cuff, but merely folds in a random or accordianfashion, as shown. The outlet connector 300 directly attaches the outletof the flexible diaphragm 298 to an inlet 302 of the flexible bag 22located at the top 304 of the bag 22 rather than at its front wall 128.An inlet connector 306 is directly connected to the end 166 of thedrainage tube 30. Relative lateral movement of the first and secondconnectors beyond a preselected limit is prevented by means includingblocking arms 308, and relative rotary movement beyond a preselectedlimit is restrained by means including a pair of restraint members 310which cooperate with radial vanes 312.

Advantageously, because of the improvement of accuracy obtained as aresult of the force isolation system, an improved method of weighingurine collected from a patient is provided. In prior weighing systems,because of the unknown magnitude of extraneous forces applied to thecollection bag and weighing apparatus by the urine delivery system,urine entered into the collection bag upon catherization and beforemounting of the collection bag to the weighing apparatus, was notaccurately weighed. It is not accurately weighed in prior devicesbecause of the need of first zeroing the weighing apparatus to insurethe degree of accuracy needed for flow rate and other measurements.Offsetting the determined weight before attachment of the bag to zerothe weighing apparatus for empty bag weight is preferred. However, inthe method provided here, the step of zeroing after mounting thecollection bag is eliminated, so that the urine collected prior tomounting may be accurately weighed and volume determined.

In particular, a method for weighing a volume of fluid is providedcomprising the steps of (a) predetermining the weight of the urinecollection bag 22 based on an average bag weight of a large sample ofsubstantially identical bags, (b) offsetting the determinant weight ofthe bag 22 from the weighing apparatus of the AUOM unit 20, (c)connecting the downstream end 166 of the drainage tube 30 to an inlet132 of bag 22 by means including the force isolation system 26 tosubstantially mechanically isolate the bag 22 and the weighing apparatusto which it is connected from forces due to the interconnection of thebag 22 and the end 166 of tube 30, (d) attaching the bag 22 to the bagmounting assembly 50 to be weighed, and (e) entering the urine to beweighed into the bag 22 through tube 30 and the force isolation system26.

Thus, the urine which may enter the collection bag 22 before the bag 22is attached to the bag mounting assembly 50 is weighed because theweighing apparatus is not zeroed to cancel out the weight of thispreviously collected urine. Accordingly, the AUOM unit weighs ittogether with the urine subsequently collected to give a combined weightor volume indication.

While a particular embodiment has been shown, it should be appreciatedthat variations may be made with regard thereto without departing fromthe scope of the invention. For instance, although a flexible plasticbag 22 has been disclosed for collecting urine, it should be clear thatmany of the advantageous features of the invention could be successfullyemployed with rigid fluid containers or container and collection systemsfor other types of biological fluids, such as blood. Thus, the scope ofthe invention is defined by the following claims and not by theforegoing detailed description of the preferred embodiment.

I claim:
 1. Apparatus for measuring the weight of fluid entering acontainer of a system obtained from the downstream end of a fluiddrainage tube, comprising:a weighing apparatus having a frame and aweighing mechanism which moves relative to the frame during changes ofthe weight being weighed thereby; means for connecting the container tothe weighing mechanism to be weighed thereby, said container moving withthe weighing mechanism relative to the frame as increasing amounts offluid are introduced into the container; means for holding thedownstream end of the tube against movement relative to the frame; andmeans for coupling the drainage tube with the container for relativefluid communication therewith including means for substantiallymechanically isolating the end of the tube from application ofsignificant force to the container whereby the accuracy of themeasurement of the weight of the container and its contents is notsignificantly affected by the coupling means.
 2. The apparatus of claim1 in which said isolation means includes a flexible memberinterconnecting the end of the drainage tube to the container.
 3. Theapparatus of claim 2 in which said isolation means includes a pair ofrelatively rigid connector members for respectively connecting oppositeends of the isolation means to an opening in the container and to theend of the drainage tube.
 4. The apparatus of claim 3 in which the oneof the connectors connecting the isolation means to the drainage tube isa connector for mating connection with the downstream end of thedrainage tube.
 5. The apparatus of claim 1 in whichsaid container is aflexible bag, and said connecting means includes means attached to theone of said pair of connectors for suspending the bag from the weighingmechanism to move therewith.
 6. The apparatus of claim 1 in which saidisolation means includesa first relatively flexible member secured tothe container and having an inlet opening therethrough, and a secondconduit interconnecting the end of the tube to the inlet opening.
 7. Theapparatus of claim 6 in whichsaid container is a flexible bag, and saidfirst relatively flexible member has greater flexibility than most ofthe bag.
 8. The apparatus of claim 6 in which said connecting meansincludesa relatively rigid connector which is fixedly attached to thecontainer and substantially surrounds said first relatively flexiblemember, and means for releasible connection of the connector to theweighing apparatus.
 9. The apparatus of claim 1 in which the conduit issubstantially cylindrical.
 10. The apparatus of claim 1 in which saidcontainer is a flexible bag with a top and a front and said couplingmeans couples the drainage tube to an inlet opening at the top of thebag.
 11. The apparatus of claim 1 in which said isolating meanscomprises means for flexibly coupling the end of the drainage tube tothe container.
 12. The apparatus of claim 1 in which said weighingapparatus includes a transducer responsive to force applied to it toproduce a representative electrical signal.
 13. A container assembly forbiological fluids, comprising:a hollow container body having an inletopening for receipt of fluids therewithin, an inlet connector forconnection with the end of a drainage tube, and means for substantiallymechanically isolating the container body at the inlet opening fromrelative movement of the inlet connector, said isolating means includinga flexible conduit for interconnecting the inlet connector and the inletopening, said conduit having a flexibility sufficient to prevent it frommechanically conveying significant force in a direction along theconduit.
 14. The container assembly of claim 13 in which said containerbody is a flexible plastic bag.
 15. The container assembly of claim 14including a mounting member associated with the isolation means andattached to the container body for mounting it to a fixture.
 16. Thecontainer assembly of claim 15 in which said mounting member has meansfor suspending it, and thus the container body, from a fixture.
 17. Thecontainer assembly of claim 15 in which said mounting member is attachedto the container body adjacent the inlet opening.
 18. The containerassembly of claim 17 in which said mounting member has means forsuspending it and thus the container body from a fixture.
 19. Thecontainer assembly of claim 13 in which the flexible conduit issubstantially non-resilient.
 20. The container assembly of claim 13 inwhich the flexible conduit is substantially resilient.
 21. The containerassembly of claim 13 in which said container body is a flexible bag witha top and a front and said inlet is at the top.
 22. The containerassembly of claim 13 including a weighing apparatus having a transducerresponsive to force applied to it for providing a signal representativeof weight.
 23. A method of weighing a volume of fluid, comprising thesteps of:predetermining the weight of a fluid container; offsetting thedetermined weight of the container from a weighing apparatus to zero theweighing apparatus; connecting the downstream end of a drainage tube toan inlet opening of the fluid container by means for substantiallymechanically isolating the container and the weighing apparatus fromforces due to the interconnection of the container and the end of thetube; attaching the container to the weighing apparatus to be weighedthereby; entering the fluid to be weighed into the container through thedrainage tube and said isolation means; and weighing the container andfluid therein.
 24. The method of claim 23 including the steps ofenteringsome of the fluid into the container after determining the amount ofoff-set to zero the weighing apparatus to compensate for the weight ofthe container and before the step of attaching the container to theweighing apparatus to be weighed thereby, and then obtaining from theweighing apparatus the combined weight of the fluid entered into thecontainer before and after the step of attaching the container to theweighing apparatus prior to further zeroing of the weighing apparatus.25. The method of claim 24 in which said step of entering some of thefluid into the container includes the step of connecting the upstreamend of the drainage tube in fluid communication with an in vivo fluidsource.
 26. The method of claim 25 in which said step of connecting theupstream end of the drainage tube includes insertion of a urinarycatheter.